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CURLOPT_CAINFO(3) libcurl CURLOPT_CAINFO(3)
CURLOPT_CAINFO - path to Certificate Authority (CA) bundle
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CAINFO, char *path);
Pass a char * to a null-terminated string naming a file holding one or
more certificates to verify the peer with.
If CURLOPT_SSL_VERIFYPEER(3) is zero and you avoid verifying the
server's certificate, CURLOPT_CAINFO(3) need not even indicate an
This option is by default set to the system path where libcurl's CA
certificate bundle is assumed to be stored, as established at build
If curl is built against the NSS SSL library, the NSS PEM PKCS#11
module (libnsspem.so) needs to be available for this option to work
properly. Starting with curl 7.55.0, if both CURLOPT_CAINFO(3) and
CURLOPT_CAPATH(3) are unset, NSS-linked libcurl tries to load
libnssckbi.so, which contains a more comprehensive set of trust
information than supported by nss-pem, because libnssckbi.so also
includes information about distrusted certificates.
(iOS and macOS) When curl uses Secure Transport this option is
supported. If the option is not set, then curl will use the
certificates in the system and user Keychain to verify the peer.
(Schannel) This option is supported for Schannel in Windows 7 or later
but we recommend not using it until Windows 8 since it works better
starting then. If the option is not set, then curl will use the
certificates in the Windows' store of root certificates (the default
The application does not have to keep the string around after setting
The default value for this can be figured out with CURLINFO_CAINFO(3).
Built-in system specific. When curl is built with Secure Transport or
Schannel, this option is not set by default.
All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_CAINFO, "/etc/certs/cabundle.pem");
ret = curl_easy_perform(curl);
For the SSL engines that do not support certificate files the
CURLOPT_CAINFO(3) option is ignored. Schannel support added in libcurl
Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if
not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.
CURLOPT_CAINFO_BLOB(3), CURLOPT_CAPATH(3), CURLOPT_SSL_VERIFYPEER(3),
ibcurl 8.1.2 April 26, 2023 CURLOPT_CAINFO(3)